Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions for Biology

What is the cross between the progeny of F₁ and the homozygous recessive parent called? How is it useful?

Name any three viruses which have RNA as the genetic material.

During the course of evolution why DNA was chosen over RNA as genetic material? Give reasons by first discussing the desired criteria in a molecule that can act as genetic material and in the light of biochemical differences between DNA and RNA.

For the MN-blood group system, the frequencies of M and N alleles are 0.7 and 0.3, respectively. The expected frequency of MN-blood group bearing organisms is likely to be ______.

Which type of selection explains industrial melanism observed in moth, Biston bitularia?

In a certain population, the frequency of three genotypes is as follows:

What is the likely frequency of B and b alleles?

Among the five factors that are known to affect Hardy-Weinberg equilibrium, three factors are gene flow, genetic drift and genetic recombination. What are the other two factors?

State and explain any three factors affecting allele frequency in populations.

Gene flow occurs through generations. and can occur across language barriers in humans. If we have a technique of measuring specific allele frequencies in different population of the world, can we not predict human migratory patterns in pre-history and history? Do you agree or disagree? Provide explanation to your answer.

Enumerate three most characteristic criteria for designating a Mendelian population.

“Migration may enhance or blurr the effects of selection”. Comment.

Name the law that states that the sum of allelic frequencies in a population remains constant. What are the five factors that influence these values?

An infertile couple was advised to undergo In vitro fertilization by the doctor. Out of the options given below, select the correct stage for transfer to the fallopian tube for successful results.

How is Hardy-Weinberg’s expression “(p² + 2pq + q²) = 1” derived?

List any two factors that can disturb the genetic equilibrium.

Trace the events from copulation to zygote formation in a human female.

Given below are Column A with a list of certain Assisted Reproductive Technologies (ART) and in Column B the procedures followed during ART:

Choose the option where ART correctly matches with the procedure.

"It is sometimes observed that the F₁ progeny shows a phenotype that resembles both the parents." Explain this type of inheritance using the example of A, B, and O blood groups in human.

At a particular locus, the frequency of allele A is 0.8, and that of allele a is 0.2. What would be the frequency of heterozygotes in a random mating population at equilibrium?

The graphs below show three types of natural selection. The shaded areas marked with arrows show the individuals in the population who are not selected. The dotted vertical lines show the statistical means.

character Graph A	character Graph B	character Graph C

1. What names are given to the types of selection shown in graphs A, B and C?
2. After the selection has operated for several generations in the above populations indicated as, Graph A, B and C, graphically illustrate the probable results.